I have no clue really what they can do other than the obvious back up. I have the iMac desktop which i use as a main & keep all my pics on etc & its got all my itunes purchases etc that i would hate to lose. We have 2 running desktops but the only thing really my hubby would wish on his, is to keep his fav settings & websites. He doesnt have pics etc on it. He also has a Macbook Air & I have a Macbook but we havent up till now used them in any way other than for mobile usage, I would kind of like to start using my macbook more for home movies editing as its a newer system & has ilife 09 etc. Anyway, what can be recommended? can 1 hardrive be used to back up 2/3 computers? Can anyone suggest a particular one?